In a transmission, it is desirable to have an indication of whether gears are fully engaged or disengaged. This information may be useful in either an open-loop or a closed-loop control system. In an open-loop transmission system, current gear position may be determined prior to commencing gear engagement. For example, in a shift rail transmission, the current position of each shift rail may be used to verify the appropriateness of translating one of the shift rails to a new position. Further, in an open loop shift rail transmission system, the duration of shift rail translation or travel from one position to another in response to a movement command of a specified duration may be used to update the command duration for subsequent shift rail movement. In a closed loop transmission system, gear or shift rail position may be used as feedback in the closed loop control so that, instead of asserting a movement command for a specified duration, the shift rail translates or travels until it reaches the desired position as indicated by the position sensor feedback.
A control system may include a system controller, further including a processor generating control signals and monitoring feedback signals. Multiple sensors may be employed to provide accurate position information, and the information from each sensor may be further used to cross-check the information from other sensors.
Accurate position information generally requires the use of several position sensors. However, in a system where cost, space, weight and the like may be constraining factors having too many sensors can be an issue. Therefore, it is desirable to minimize the number of sensors and the number of wires that must be run to the sensors potentially while still promoting redundancy in case one or more sensors fails.